2aSC4. The roles of category boundaries and prototypes in the perception and production of speech and language.

Session: Tuesday Morning, December 3

Time: 8:50

One of the fundamental issues in the study of speech perception is to model
the cognitive process of phonetic judgment and to infer the underlying
mechanism. Experimental results on categorical judgment as well as on judgment
of typicality do not attest to the existence of a single prototype for each
phonetic category, but rather to the existence of a continuum of exemplars,
viz., a region of high typicality, whose shape is not necessarily convex, in the
multidimensional space of acoustic/phonetic parameters. The neural mechanism for
separating such a region from others is based on thresholds (i.e., boundaries),
but not on distances from a single point of reference. On the other hand, the
production of a specific phone in a given context by a single speaker displays a
very sharp distribution, which indicates the existence of a speaker-specific
prototype in speech production. Such an apparent asymmetry of production and
perception is shown to exist also in the use of language, and can be explained
in the light of a general underlying mechanism for coding and decoding the
information. Implications of these results to spoken language processing will
also be discussed.